Electrolytic recovery cell

ABSTRACT

An efficient electrolytic recovery cell which has an anode, a cathode surrounding the anode, and a pump adjacent the cathode for directing a flow of electrolyte into the space between the anode and the cathode. The pump directs the flow of electrolyte in a generally horizontal direction to cause electrolyte to helically descend between the anode and the cathode. The pump has a hollow tube connected to it and running adjacent the cathode to recirculate the electrolyte coming from the bottom of the cathode.

Nov. 14, 1972 H. MANDROIAN ELECTROLYTIC RECOVERY CELL Filed 001:. 28, 1970 `l' Q Qdb 26h A E 1 f2- Za 3? 'QQ '3o QQ 26a@ IQcL 29 f IOQ I4 82 United States Patent O U.S. lCl. 20d-237 12 Claims ABSTRACT F THE DISCLOSURE An efficient electrolytic recovery cell which has an anode, a cathode surrounding the anode, and a pump adjacent the cathode for directinga iiow of electrolyte into the space between the anode and the cathode. The pump directs the iiow of electrolyte in a generally horizontal direction to cause electrolyte to helically descend between the anode and the cathode. The pump has a hollow tube connected to it and running adjacent the cathode to recirculate the electrolyte coming from the bottom of the cathode.

BACKGROUND OF THE INVENTION (l) Field of the invention This invention relates to electrolytic apparatus for recovering products from electrolytic solutions.

(2) Description of the prior art It is well known in the art to recover products from solutions by an electrolytic process. This well known process, simply stated, involves immersing a pair of electrodes in an electrolytic solution containing the product to be recovered and impressing across the electrodes a voltage of suicient magnitude to cause electrolytic decomposition of the desired product. One use of the electrolytic recovery process, for example, is recovering silver from used photographic hypo solutions.

While there are many coniigurations of electrolytic cells to be found in the art, the simplest type involves one such as described in an issued patent to N. J. Cedrone, U.S. Pat. No. 3,003,942, issued Oct. 10, 1961, entitled Electrolytic Cell for Recovery of Silver from Spent Photographic Fixing Baths. This patent discloses the use of a cylindrical tank having as its cathode a steel cylinder and as its anode an internal smaller cylinder of carbon. A recirculating pump external to the tanks is provided which pumps electrolyte from the bottom of a collection tank upon which the cylindrical tank is located into two inlets 180 apart at the bottom of the cylindrical tanks. The pump action causes the electrolyte to spiral upwards between the anode and the cathode to the top of the tank, over the top of the cylindrical carbon anode and down through a filter bag into the collection tank to be once again pumped back into the steel cathode cylinder. Since, however, the pumping system for this apparatus is completely external to the container holding the electrolyte, several deficiencies occur in operation. The external pump configuration used by Cedrone is highly prone to leakage problems which are intolerable in a commercial electrolytic recovery system which would be used in photography studios, hospitals, etc. Additionally, because of the length of tubing through which it is required to pump the electrolyte, a relatively high pressure pump, i.e. over p.s.i., must be employed to overcome the loss in pressure as the electrolyte flows through the tubing, thus increasing the probability of leakage problems. Such a high pressure pump makes the system even more prone to leakage and is also uneconomical since it requires a relatively large amount of power for its operation. Finally, since the high pressure pump puts out a relatively low volume of fluid,

r ICC the interspace between the anode and the cathode must remain relatively small to insure a swift liow of electrolyte, thereby greatly increasing the probability of an electrical short occurring between the anode and the cathode due to metallic whiskers growing on the surface of the cathode and making contact with the anode.

OBJECTS AND SUMMARY OF THE INVENTION 4The principal object of the present invention is to provide an electrolytic apparatus for recovering products from electrolytic solutions which apparatus :avoids the pumping deficiencies of the prior art recovery apparatus. A more specic object of the invention is to provide an electrolytic recovery apparatus which employs a large liow, Ilow pressure pump.

Another object of the invention is to provide an electrolytic recovery apparatus in which the pump is located internally of the container for the anode, cathode and electrolyte.

In accordance with one embodiment of the present invention, an electrolytic recovery cell is provided which has a cylindrical cathode surrounding an anode both of which are immersed in an electrolyte inside a container. A high volume, low pressure pump is located adjacent the cathode and is provided with a hollow tube extending the length of the cathode to the bottom of the container. The cathode and the tube have corresponding openings at the top and the bottom edges thereof so that the pump can continuously draw electrolyte from the lower end of the cathode and discharge it through the tube into the top end of the cathode in a generally horizontal direction to cause the electrolyte to helically descend between the anode and the cathode. The cathode may be supported on a platform in the container and a hole provided in the platform adjacent the end of the tube to permit electrolyte between the walls of the container and the cathode to be recirculated by the pump. Additionally the container may have an opening substantially coaxially aligned with the tube to permit the introduction of fresh electrolyte into the pumping system.

The novel features of the invention are set forth with particularly in the appended claims. The invention will best be understood from the following description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side sectional view of a first embodiment of the invention;

FIG. `2 is a top sectional view of the embodiment of FIG. 1 along the line 2 2;

FIG. 2a shows a variation of the embodiment illustrated in FIGS. 1 and 2.

FIG. 3 is a perspective, partially cut away view of a second embodiment of the present invention;

FIG. 4 i's` a sectional top view of the embodiment of FIG. 3 along the line 3 3;

FIG. 5 is a top sectional view of a third embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, a iirst embodiment of the present invention is illustrated. A container 10 is provided into which is placed a cathode 12, which is generally cylindrical and can be made of stainless steel, and an anode 14 which generally takes the form of a carbon rod. Adjacent the upper end of the cathode 12 is a pump 16 which consists of a motor 18, an impeller 20 and a hollow tube 22, the hollow tube extending parallel and adjacent to the cathode 12. The cathode 12 is provided with openings 24a and 24b at the top and bottom extremities thereof adjacent the tube 22. The tube 22 is provided with openings 26a and 26b located adjacent the openings 24a and 24b. A voltage V is impressed across the anode 14 and the cathode 12 to cause electrolysis to take place in the electrolyte 28. If a photographic hypo solution is used for the electrolyte 28, a layer of silver will be deposited on the inner surface of the cathode 12.

In operation, the pump 6 directs a flow of electrolyte 28 into the space between the anode 14 and the cathode 1'2. This 4flow is in a generally horizontal direction, perpendicular to the axis of the anode 14 and the cathode 12, and causes the electrolyte to helically descend between the anode and the cathode. The helical motion of the electrolyte may be enhanced by the addition of a deector 29 (shown in FIG. 2). At the same time, electrolyte 28 is being drawn through holes 2 4b and 26b into the tube 22 by action of the pump 16. When the electrolyte 28 reaches the top of tube `22 it is directed through openings 26a and 24a back onto the top portion of the space between anode 114 and cathode 12. Since the pump is 1ocated adjacent cathode 12 and since there is little to no constriction of the ow between tube 22 and cathode 12, a low pressure, high volume pump, of the order of .1 p.s.i., can be used. In addition, since there is very little pressure loss on the recirculation path through tube 22 from cathode 12, the efficiency of pump 16 is greatly enhanced. Thus because of the pump position and the recirculation configuration of the present invention, a large volume of electrolyte 28 can be pumped into the spacing between the anode 14 and cathode 12 to avoid a deficiency in the electrolyte 28 of, for example, silver cations, and to allow higher plating current and higher plating quality. In addition, since a low pressure system can now be employed, the problem of electrolyte leakage is completely avoided.

In FIG. 2, taken along line 2-2 of FIG. 1, the intimate relationship of tube 22 and cathode 12 is illustrated more graphically with the holes 24a and 26a being nearly coupled to one another. yIf it is not desired to have a separate return tube 22, cathode i12 and container 10 can be placed in contact with one another, as shown in FIG. 2a, at points 30 and 32. Thus portion 10a of container and portion 12a of cathode 12 would serve to form a relatively uid-tight channel means for the recirculation path of the electrolyte 28, the pumping force being provided by impeller of pump 16.

While the pump 16 is shown as pumping electrolyte 28 into the upper ends of anode 14 and cathode -12, a like efliciency of operation would result if openings were made in the central region of cathode 12 and tube 22 and the electrolyte v28 were pumped into the center of cathode 12. A portion of the electrolyte 28 would then spiral upwardly and pass through openings 24a and 26a into (and down) tube 22, while the balance would spiral downwardly and pass through openings 24b and 26b into (and up) tube 22, all to be recirculated into the central region of cathode 12. In addition, although the pump 16 and the channel means is shown adjacent cathode 12, they could just as simply be placed adjacent anode 14. In this embodiment anode 14 would be made hollow with suitable openings therein at the top and bottom thereof. The impeller 20 of pump 16 and tube 22 would then be placed in the hollow region of anode 14 to recirculate the electrolyte 28. Alternatively, anode 14 alone could be used in place of tube 22 as the channel means for the recirculation by pump |16 of the electrolyte 28.

In FIGS. 3 and 4 a second embodiment of the invention is shown. A container 10, mounted on legs l40, contains an electrolyte 28, a pair of cathodes 12 and 12', a pair of anodes 14 and 14', and a single pump 16 comprising a motor y18, an impeller 20 and a hollow tube 22. As in the embodiment shown in FIGS. 1 and 2, the pump 16 acts to recirculate the electrolyte 28 through the spacings between the cathodes 12, 12 and the anodes 14, 14. In the tube 22, a single hole 26a is provided to direct the pumped electrolyte 28 through holes 24a and 24a into the upper spacings between the cathodes 12, 12' and the anodes 14, 14', the action of the pump 16 causing a clockwise ilow of the electrolyte 28 in the cathode i12 and a counterclockwise flow of the electrolyte 28 in the cathode 12'. At the lower end of the cathodes 12, 12 a single hole 26b in the tube 22 serves to receive the electrolyte 28 from the cathodes 12, 12' through holes 24b, 24b in the lower portions of the cathodes 12, l12'.

In the embodiment shown in FIG. 3, the cathodes 12, 12 are positioned on a platform` 34 mounted on legs 36 in the bottom of the container 10. An opening 38 is provided in the platform 34 below the bottom opening of the tube 22. As a result of this opening 38, the electrolyte between the walls of the container 10 and the walls of the cathodes 12, 12 is caused to be recirculated by the pump 16. It should be noted that the platform 34 could be eliminated by suspending the cathodes 12, 12 above the bottom of the container 10 or by providing additional holes in the lower ends of the cathodes 12, '12'. In addition, an opening 42 is provided in the bottom of the container 10 directly below the opening 38 and substantially coaxially aligned with the tube 22. This opening 42 permits the introduction of fresh electrolyte into the recirculating system to be pumped by the pump 16. Tube 44 is provided to draw off excess electrolyte 28.

In FIG. 5 a third embodiment of the invention is illustrated. A container 10 contains four cathodes 12, 12', 12, 12"', and four corresponding anodes, 14, 14', 14", 14'". The cathodes are arranged in such a manner as to be in contact with one another to form a relatively fluidtight channel means 46. The electrolyte 28 pumped up the channel means 46 by means of the impeller 20 flows into the cathodes through openings 24a, 24a', 24a", 24a'" to cause the electrolyte 28 to helically descend between the cathodes and the anodes in a counterclockwise manner in cathodes 12 and 12 and a clockwise manner in cathodes 12 and 12". In a like manner, it should be noted that the cathodes 12 and 12 in FIG. 4 could be placed in contact with the wall of container 10 and the electrolyte 28 pumped up by the impeller 20 through a channel means consisting of a portion of the wall of container 10 and a portion of the surfaces of the cathodes 12 and 12. In addition, it can be readily seen that three cathodes can be configured to provide a channel means therebetween for the recirculation of the electrolyte 28.

Although particular embodiments of the invention have been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art and, consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.

What is claimed is:

1. An electrolytic recovery cell comprising:

a cathode;

an anode positioned within said cathode;

pump means operable for directing a ow of electrolyte into the space between said anode and said cathode; and

channel means substantially vertical and substantially parallel and in close proximity to said cathode for directing the ow of said electrolyte, said pump means operating in conjunction with said channel means to recirculate said electrolyte.

2. The cell of claim 1 further including two or more cathodes, each cathode having an anode therein, said cathodes being positioned with respect to one another to form said channel means.

3. The cell of claim 1 further including container means for said cathode and anode, said cathode and said container means being positioned with respect to one another to form said channel means.

4. The cell of claim 1 wherein said channel means comprises a hollow tube.

5. The cell of claim 4 wherein said cathode has an opening in the lower end thereof and wherein said hollow tube has a corresponding opening in the lower end thereof to receive electrolyte from said lower opening in said cathode to recirculate said electrolyte.

6. The cell of claim 4 further including container means and platform means inside said container means for supporting said cathode, said platform means having an opening therein coupled to said tube to permit electrolyte between the walls of said container means and said cathode to be recirculated by said pump means.

7. The cell of claim 6 wherein said container means has an opening substantially coaxially aligned with said tube to permit the introduction of electrolyte to be pumped by said pumping means.

8. An electrolytic recovery cell comprising:

a container,

a platform in said container,

one or more cylindrical cathodes supported on said platform and being removable from said container, anode means inside said cathodes,

means for supporting said anodes,

pump means adjacent said cathodes and including a hollow tube adjacent said cathodes and parallel thereto, said cathodes and said tube having corresponding openings in the upper and lower portions thereof to allow electrolyte to be pumped in a recirculating manner from the bottom of said cathodes to the top of said cathodes and said platform having an opening therein coupled to said tube to permit electrolyte between the walls of said container and said cathodes to be recirculated by said pump means.

9. A recirculating system for an electrolytic recovery cell comprising:

one or more cathodes having anodes positioned therein;

pump means operable for directing a flow of electro- 6 lyte in the space between said anodes and said cathodes; and

channel means substantially vertical and substantially parallel and in close proximity to said cathodes for directing the flow of said electrolyte, said pump means operating in conjunction with said channel means to recirculate said electrolyte.

10. The recirculating system of claim 9 wherein said channel means comprises a hollow tube.

11. The recirculating system of claim 9 further comprising container means for said cathodes and anodes, said channel means including a portion of the surfaces of one of said cathodes and said container means.

12. The recirculating system of claim 9 wherein said channel means comprises a portion of the surfaces of at least three of said cathodes.

References Cited UNITED STATES PATENTS 3,003,942 10/1961 Cedrone 204--109 X 3,551,317 12/1970 Cooley 204-273 X 2,997,438 8/ 1961 James et al. 204--273 3,560,366 2/ 1971 Fisher 204-109 X 3,583,897 6/1971 Fulweiler 204-109 X FOREIGN PATENTS 916,438 1/ 1963 Great Britain 204-272 1,123,168 8/ 1968 Great Britain 204-272 JOHN H. MACK, Primary Examiner D. R. VALENTINE, Assistant Examiner U.S. Cl. XR. 

